ENSO variability has a high impact on climate everywhere. Thus many problems in climatology require a good quantification of ENSO variability. One such quantification is the calculation of the Multivariate ENSO Index (MEI).
The MEI is the leading EOF computed from several variables. For this exercise, use Era Interim data for sea level pressure, sea surface temperatures, and zonal and meridional near surface wind speeds.
You will base your calculations on the above mentioned variables. Conduct an EOF analysis on the different variables for the region 30°S-30°N and 100°E-70°W. The EOFs should be calculated for 12 overlapping bi-monthly “seasons” (Dec-Jan, Jan-Feb, Feb-Mar,…, Nov-Dec). The result will be an index time series and loading patterns for the first EOF.
Hint: Resources by NOAA may help.
Optional: Investigate the other EOF patterns - can you interpret any of them?